[libvirt] [PATCH v4 0/8] Add support for taking screenshots of domain console

[Daniel P. Berrange]

On Fri, May 13, 2011 at 05:15:56PM -0600, Eric Blake wrote:
> On 05/13/2011 02:56 AM, Daniel P. Berrange wrote:
> > On Fri, May 13, 2011 at 10:34:24AM +0200, Michal Prívozník wrote:
> >>> Then, screen is calculated as
> >>>
> >>>   Screen  Device  Head
> >>>    0      video0  0
> >>>    1      video0  1
> >>>    2      video1  0
> >>>    3      video1  1
> >>>    4      video1  2
> >>>    5      video1  3
> >>>
> >>>
> >>>
> >>> Incidentally an RFE is needed against QEMU, since it can only do screen
> >>> dump of the first device :-(
> >>>
> >>> Daniel
> >>
> >> Yes, that is what I had in my mind when creating this concept.
> > 
> > Ok, please document that in the API docs for the public API
> > 
> >> Or would it be better to split screen ID into video # and head #?
> > 
> > No, I think that's probably overkill, unless anyone can think of
> > something we can do with them separated, that we can't do with them
> > combined...
> 
> Good thing we have the flags argument.  When you have a card that
> supports multiple monitors, I could see it being worth capturing a
> screenshot of just one monitor, vs. a combined screenshot of both
> monitors as a single image.  With the above layout, this could be done as:
> 
> virDomainScreenshot(dom, st, 1, 0) - just screen 1 (head 1 of video0)
> virDomainScreenshot(dom, st, 1, VIR_DOMAIN_SCREENSHOT_DEVICE) -
> composite of all screens on video1 (that is, screens 2-5)
> 
> of course, supposing that the hypervisors support combined imaging.

The only way I could see that being possible, is if there was actually
a guest OS agent that captured the screenshot, because the hypervisor
has no way of knowing what the layout of the screens are. ie if the
device has 2 outputs and you want a single image of both outputs
how do you know if the output 1 is left of output 2, or right of it,
or above it, or below it, etc.

Daniel
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